Have you considered that you might not have enough visibility into what they do to be able to judge? Obviously the percentage of useless work is >0% but you are just throwing numbers around.
As someone who has worked a bullshit cyber security job in government, I will say 50% is a conservative estimate. Our team had 9 people in it: 1 manager, 6 junior-mid level engineers and 2 senior engineers. The only ones that did any actual work were the senior engineers. The junior-mid engineers literally did nothing for months on end. The manager would disappear all week only to turn up on Friday mornings to give "corporate update" presentations to the team.
